A dielectric material is a material in which polarization is generated when an electric field is applied thereto, and is used in electronic devices because the dielectric material serves to stabilize power supply by storing a predetermined amount of electricity when the dielectric material is used as a capacitor and alleviate an influx of sparks into a circuit in an alternating current power supply.
Existing ceramic capacitors are classified into Class I and II. Class I is for temperature compensation, has a very small capacitance change rate according to the temperature, and good high-frequency characteristics, and uses a paraelectric such as (Ca,Sr)(Ti,Zr)O3. Class II is for temperature compensation and has an aspect in which a change in dielectric constant according to the temperature is large and change widths in dielectric constant and dielectric loss under alternating and direct current voltages are large, but has a high dielectric constant value and uses a ferroelectric such as (Ba,Ca)(Ti,Zr)O3.
In the early period of development of ceramic capacitors in order to develop a high capacitance capacitor, studies using Pb(Ti, Zr)O3 having a relative dielectric constant of approximately 200,000 as a base material have been conducted, but due to problems in that lead is hazardous to the environment and human bodies, studies using (Ba,Ca)(Ti,Zr)O3 which is Class II for a high dielectric constant, and the like as a base material have been actively conducted.
Currently, in order to improve the relative dielectric constant and enhance temperature stability, studies in which various additives are mixed or a core-shell structure is formed or subjected to grain boundary segregation during a heat treatment process after additives are mixed, or studies in which a heat treatment is performed by chemically coating an initial powder, and then preparing a molded body have been mainly conducted.
Recently, as electronic devices have been rapidly reduced in size due to the development of technology, industrially used capacitors are greatly required to have high capacitance and achieve reduction in size. That is, there is a need for developing a dielectric material which is used in a stack-type ceramic capacitor due to the high relative dielectric constant, or has small particles for reduction in size of a capacitor.
In a grain boundary insulation-type capacitor consisting of semiconducting particles and insulating grain boundaries, it is assumed that capacitors at the grain boundary are connected in series. In this case, a capacitance, which is a physical quantity exhibiting an ability of an object to accumulate electric charge, is a value obtained by dividing the number of capacitors connected in series in the capacitance of a grain boundary. When the thickness of a sample is dc, the size of a particle is db, the thickness of a grain boundary is dgb, the relative dielectric constant of the grain boundary is εgb , and the surface area is A, the number of capacitors connected in series, n is
  n  =            d      c              d      b      and the capacitance of a grain bound, Cgb is
  Cgb  =            ɛ      0        ⁢          ɛ      gb        ⁢          A              d                  gb          ⁢                                                    
Accordingly, the total capacitor of n capacitors of the capacitance Cgb, which are connected in series, is
                    C        =                ⁢                              C            gb                    n                                        =                ⁢                                                            ɛ                0                            ⁢                              ɛ                gb                            ⁢              A                                      d              gb                                ⁢                                    d              b                                      d              c                                          and the apparent dielectric constant, εapp is
      ɛ    app    =            ɛ      gb        ⁢                  d        b                    d        gb            
In order for the capacitor to achieve reduction in size and have a high capacitance, the particle size (db) needs to be small, but when the particle size becomes small, there is a problem in that the apparent dielectric constant (εapp) also becomes small.